In the future access networks a mobile node may transmit/receive data through a number of PoANs (Point of Attachment to the Network) based on different access technologies. The access aggregation network connecting PoANs uses L2 (Layer 2 of the Network Layer model) and L1 (Layer 1) devices (switches and repeaters). PoANs connected to such networks operate as L2 switches without usage of L3 (Layer 3) routing mechanisms.
The importance of pervasive connectivity to the network has increased over the last years and it is going to increase in the future. Mobile nodes with multiple network interfaces are able to access the network with a lot of advantages. Different network interfaces can then be used by a mobile node for data transmission depending on the access technology of the PoAN currently available for the user. Handover processes where the mobile node hands off between two network Interfaces of different technologies will therefore be an important issue in the future networks.
Existing mechanisms supporting handovers between different access technologies using two or more network interfaces use L3 or higher Layer methods to hand off traffic flows between two interfaces. This is because in such mechanisms each network interface of the mobile node connected to the same L2 network must have its own IP (Internet Protocol) address. Conventional IP configuration and mobility protocols like Mobile IP (MIP) or Session Initiation Protocol (SIP) do not consider the fact that different PoANs used by the mobile node can be integrated into the same converged access aggregation L2 network and one IP address may be used by all network interfaces of the mobile node in the non-simultaneous manner. The unique features of data transmission on L2 Within the converged access aggregation L2 network and over the wireless links are not taken into consideration by these prior art mechanisms. The IP address of the mobile node is therefore changed during handover between two Interfaces and mobility protocols above L2 must be applied to retain established sessions. This causes an additional handover delay and potential load in the network. For example, at least one round trip time between the mobile node and its corresponding node is required to re-establish a session using SIP or Host Identity Protocol or Stream Control Transmission Protocol and an additional overhead of at least one IP header is caused by the IP-in-IP encapsulation used by the MIP. These factors degrade the traffic performance that may therefore be unacceptable for time-critical multimedia services like IPTV (IP television) or video telephony.